The present invention relates to an endoscope device capable of performing a special light observation using specific narrow band light and wide band light such as white illumination light.
In recent years, an endoscope device capable of performing a so-called special light observation has been used, where the special light observation obtains information on a tissue at a desired depth of a living body by emitting specific narrow band light (narrow band light) to a mucous tissue of the living body. This type of endoscope device may simply visualize living body information, which cannot be obtained from an ordinary observation image, by emphasizing a lesion and a microstructure of a surface layer of a new blood vessel generated at, for example, a mucous layer or a lower mucous layer. For example, when an observation subject is a cancer lesion, if narrow band blue light (B) is emitted to the mucous layer, the microstructure or the microscopic blood vessel of the surface layer of the tissue may be observed in more detail, so that the lesion may be more accurately diagnosed.
On the other hand, an invasion depth of light in the thickness direction of the living body tissue is dependent on the wavelength of the light. In the case of the blue light (B) having a short wavelength, the light only reaches the vicinity of the surface layer due to the absorbing and scattering characteristics of the living body tissue, and is absorbed and scattered at the depth range, so that the light may be observed as returned light mainly including information on the surface layer tissue. In the case of green light G having a wavelength longer than that of the B light, the light reaches a position deeper than the range the B light reaches, and is absorbed and scattered at this range, so that the light may be observed as returned light mainly including information on the intermediate layer tissue and the surface layer tissue. In the case of red light (R) having a wavelength longer than that of the G light, the light reaches a deeper position of the tissue, and is absorbed and scattered at this range, so that the light may be observed as returned light mainly including information on the deep layer tissue and the intermediate layer tissue.
That is, image signals obtained by receiving light using an imaging sensor such as a CCD after emitting the B light, the G light, and the R light respectively mainly include information on the surface layer tissue, information on the intermediate layer tissue and the surface layer tissue, and information on the deep layer tissue and the intermediate layer tissue.
For this reason, in the special light observation, in order to easily observe the microstructure or the microscopic blood vessel of the tissue surface layer of the living body tissue, only two types of narrow band light, that is, the narrow band light of blue (B) suitable for observing the surface layer tissue and the narrow band green light G suitable for observing the intermediate layer tissue and the surface layer tissue are used as the narrow band light emitted to the living body tissue without using the narrow band red light R mainly suitable for observing the intermediate layer tissue and the deep layer tissue of the living body tissue. Then, image processing is performed only using a B-image signal (B narrow band data) mainly including information on the surface layer tissue and obtained by an imaging sensor after emitting the B narrow band light and a G-image signal (G narrow band data) mainly including information on the intermediate layer tissue and the surface layer tissue and obtained by an imaging sensor after emitting the G narrow band light, and an observation is performed by displaying a quasi-color image on a monitor or the like.
Therefore, in the image processing, the G-image signal (G narrow band data) obtained by the imaging sensor is allocated to R-image data of a color image through a predetermined coefficient, the B-image signal (B narrow band data) is allocated to G-image data and B-image data of a color image through a predetermined coefficient, a quasi-color image including 3-ch (channel) color image data is created, and the image is displayed on a monitor or the like.
For this reason, the image processing of the narrow band light mode converting two GB-image signals obtained by receiving the returned light of the narrow band light using the imaging sensor into RGB color image data for a quasi-color display on a display unit is different from the image processing of the ordinary light mode converting three RGB-image signals obtained by receiving the returned light of the ordinary light using the imaging sensor into RGB color image data for a color display on a display unit.
Further, even in the special light observation using the R narrow band light, the G narrow band light, and the B narrow band light, when the microstructure or the microscopic blood vessel of the surface layer tissue is observed, as described above, the image processing is performed only by using the G-image signal and the B-image signal without using the R-image signal (R narrow band data), and an observation is performed by displaying the quasi-color image on the monitor or the like.
Even in this case, in the image processing, in the same manner, the G-image signal is allocated to the R-image data, and the B-image signal is allocated to the G-image data and the B-image data, the quasi-color image including 3-ch color data is created, and the image is displayed on the monitor or the like.
As a result, in any case, since the quasi-color image displayed on the monitor or the like mainly includes the B-image signal (B narrow band data) including information on the surface layer tissue, the microstructure or the microscopic blood vessel of the surface layer tissue may be displayed in more detail, and the microstructure and the microscopic blood vessel of the surface layer tissue may be easily observed (refer to JP 3559755 B and JP 3607857 B).
In the special light observation described above, when the distance between the lesion tissue and the special light irradiation position is small, the microstructure or the microscopic blood vessels of the surface layer tissue, which may be easily brightly seen, may be displayed as an image, but there is a problem in that it is more difficult to see the microstructure or the microscopic blood vessels of the surface layer tissue as the distance increases.
Further, when the distance increases as described above, the irradiation light amount is generally increased in order to handle such a problem. However, there is a limitation on the increase in irradiation light amount, particularly, an increase in special light amount. Accordingly, a problem arises in that the color tint of the captured image changes when compensating for insufficient special light amount using ordinary light.